<div dir="ltr">Hi Lupin,<br><div class="gmail_extra"><br><div class="gmail_quote">On 19 May 2017 at 13:22, Lupin Lin <span dir="ltr"><<a href="mailto:lupin@asiaa.sinica.edu.tw" target="_blank">lupin@asiaa.sinica.edu.tw</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">To the experienced user of DiFX or HOPS,<div><br></div><div><div>Sorry to spend you some time on two questions.</div><div>The first one is related to the integration time presented on the final plot after the auto- or cross- correlations.</div><div>(The DiFX I used is trunk ver. and and the HOPS ver. I used is 3.13)</div><div><br></div><div>1. </div><div>Here the GLT team recorded two signals with 3 noise sources (only 1 is the same with a potential delay less than 1 ns) from the same ROACH, and made a test in correlation.</div><div>We simply assumed that the Sky (Ref.) frequency is 230 GHz and the data were obtained from the same site (both G1 and G2 were assigned to the same position of GLT). </div><div>We correlated the data of 5-sec. supported with the zoom-band mode at 1,200-1,328 MHz.</div><div>————(Contents in .v2d file)———</div><div><div>vex = ext.vex.obs</div><div>mjdStart = 2017y124d05h42m00s</div><div>mjdStop = 2017y124d05h42m05s</div><div>antennas = G1,G2</div><div>startSeries = 7000</div><div>dataBufferFactor = 16</div><div>visBufferLength = 80</div><div>nDataSegments = 8</div><div>minLength = 0.5</div></div><div>————————————————</div><div>But according to the attached figure of “Zoom128_5sec.pdf”, the int time is only 4.995 sec.</div><div>What’s the reason to cause a loss of the obtained Int. time? </div><div></div></div></div><br></blockquote><div><br></div><div>This may be HOPS-related: I'm not an expert on HOPS so I can't comment. But another possibility is that the correlation runs from 054200 to 054205 at the geocentre, and if the recorded data duration was only 5 seconds long but at the telescope, then the geometric delay will mean than a few milliseconds of data will be chopped off. Maybe one of the HOPS users can chime in on how that integration time number is calculated in the HOPS plot - is it based on the weight? If so then my hypothesis is plausible.<br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div><div></div><div><br></div><div>2. </div><div>Following the previous test, I used Jan Wagner’s code to do the band subtraction (the original full band is 2GHz) and checked the obtained phase of different cases.</div><div>I summarized my tests and my questions in the attached file “phase.pdf”.</div><div></div></div></div><br><div style="word-wrap:break-word"><div><br><div></div><div>The 1st case is the same as shown in the attached “Zoom128_5sec.pdf”.</div><div>What’s the possible origin to cause the phase shift? </div><div>I originally suspect that such a shift is originated from the change in Sky/Ref. freq, but it might be wrong….</div><div><br></div></div></div></blockquote><div><br></div><div>I'm sorry, but I can't follow what your are trying to do here. I'm not sure what Jan's code is that you're referring to (is it something that filters e.g. your 2 GHz band down to 128 MHz in a chosen window?) If that is the case, what is the input - already quantised 2 bit VDIF data? That will lead to nasty re-quantisation errors - you'll notice that the amplitude goes down, too. <br><br></div><div>But the root of the problem is: what are you actually ultimately trying to achieve? A verification of some kind?<br><br></div><div>Cheers,<br></div><div>Adam<br></div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word"><div><div></div><div>Sincerely,</div><div><div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">--</span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">Lupin Chun-Che Lin</span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">Supporting Scientist of GLT (GreenLand Telescope) project </span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">in Institute of Astronomy and Astrophysics, Academia Sinica,</span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">14F of Astronomy-Mathematics Building (Rm: 1405), </span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">National Taiwan University. </span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">No.1, Sec. 4, Roosevelt Rd, Taipei 10617, Taiwan.</span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">Tel: <a href="tel:+886%202%202366%205464" value="+886223665464" target="_blank">+886-2-2366-5464</a></span></div><div style="font-family:新細明體,sans-serif"><span style="font-size:12px">Fax: <a href="tel:+886%202%202367%207849" value="+886223677849" target="_blank">+886-2-2367-7849</a></span></div></div></div></div></div><br>______________________________<wbr>_________________<br>
Difx-users mailing list<br>
<a href="mailto:Difx-users@listmgr.nrao.edu">Difx-users@listmgr.nrao.edu</a><br>
<a href="https://listmgr.nrao.edu/mailman/listinfo/difx-users" rel="noreferrer" target="_blank">https://listmgr.nrao.edu/<wbr>mailman/listinfo/difx-users</a><br>
<br></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr" style="font-size:12.8000001907349px"><div dir="ltr" style="font-size:12.8px"><div dir="ltr" style="font-size:12.8px"><div dir="ltr" style="font-size:12.8px"><div dir="ltr" style="font-size:12.8px">!=============================================================!<br>Dr. Adam Deller </div><div dir="ltr" style="font-size:12.8px">ARC Future Fellow, Senior Lecturer</div><div style="font-size:12.8px">Centre for Astrophysics & Supercomputing </div><div dir="ltr" style="font-size:12.8px">Swinburne University of Technology <br>John St, Hawthorn VIC 3122 Australia</div><div style="font-size:12.8px">phone: +61 3 9214 5307</div><div style="font-size:12.8px">fax: +61 3 9214 8797</div><div style="font-size:12.8px"><br></div><div style="font-size:12.8px">office days (usually): Mon-Thu<br>!=============================================================!</div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
</div></div>